Based on the surgical model using transforaminal lumbar interbody fusion (TLIF) to treat lumbar spondylolisthesis, this paper presents the investigations of the biomechanical characteristics of cage and pedicle screw in lumbar spinal fusion implant fixed system under different combinations with finite element method. Firstly, combining the CT images with finite element pretreatment software, we established three dimensional nonlinear finite element model of human lumbar L4-L5 segmental slight slippage and implant under different fixed combinations. We then made a comparison analysis between the biomechanical characteristics of lumbar motion range, stress distribution of cage and pedicle screw under six status of each model which were flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation. The results showed that the motion ranges of this model under different operations were reduced above 84% compared with those of the intact model, and the stability of the former was improved significantly. The stress values of cage and pedicle screw were relatively larger when they were fixed by single fusion device additional unilateral pedicle screw, but there was no statistically significant difference. The above research results would provide reference and confirmation for further biomechanics research of TLIF extracorporal specimens, and finally provide biomechanical basis for the feasibility of unilateral internal fixed diagonal intervertebral fusion TLIF surgery.
Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Lumbar Vertebrae ; Models, Anatomic ; Motion ; Pedicle Screws ; Posture ; Range of Motion, Articular ; Rotation ; Spinal Fusion

OBJECTIVETo analyze the forces of rotational wall vessel (RWV) bioreactor on small tissue pieces or microcarrier particles and to determine the tracks of microcarrier particles in RWV bioreactor.

METHODSThe motion of the microcarrier in the rotating wall vessel (RWV) bioreactor with both the inner and outer cylinders rotating was modeled by numerical simulation.

RESULTSThe continuous trajectory of microcarrier particles, including the possible collision with the wall was obtained. An expression between the minimum rotational speed difference of the inner and outer cylinders and the microcarrier particle or aggregate radius could avoid collisions with either wall. The range of microcarrier radius or tissue size, which could be safely cultured in the RWV bioreactor, in terms of shear stress level, was determined.

CONCLUSIONThe model works well in describing the trajectory of a heavier microcarrier particle in rotating wall vessel.

Bioreactors ; Computer Simulation ; Microspheres ; Motion ; Porosity ; Rheology ; Rotation ; Stress, Mechanical ; Tissue Engineering ; methods

Rotating wall vessels (RWVS), an ingenious apparatus for three-dimensional suspension culture, is widely used to build a simulated microgravity-effect on cell. Independent researchers have proposed hypotheses to illustrate why RWVS can simulate certain aspects of microgravity. Many of the hypotheses stated that the culture condition in RWVS is determined by the cellular mechanical environment which is a result of low fluid shear and microcarrier's motion. The microcarrier's motions consist of primary and secondary motions. In the light of the analysis of forces loaded by the microcarriers, some conclusions are drawn from the data on microcarriers' primary and secondary motions about which many simulations and observations have already been conducted.
Cell Culture Techniques ; instrumentation ; methods ; Gravitation ; Models, Theoretical ; Motion ; Rotation ; Stress, Mechanical ; Weightlessness Simulation

OBJECTIVETo study the effect of length of cervical anterior fusion on adjacent levels by Biomechanical test.

METHODSSix fresh-frozen human cervical specimens were used in this study. The specimens were tested in flexion, extension, bending and rotation on a spine 3D test system. The specimens were tested intact and then underwent a single-level anterior cervical discectomy and fusion (ACDF) at the C4-5 first, a double-level fusion at the C4-6, and finally extended to triple-level at the C4-7, Based on a hybrid test method. Changes in overall range of motion (ROM), segmental motion and facet joints pressure during flexion, extension, bending and rotation were measured and statistically analyzed.

RESULTSThe overall ROM of the entire spinal construct decreased progressively as the single-level fixation extending to 2-level and 3-level (P < 0.05). A progressive increase in ROM above (C3-4) the fused motion segment units (MSUs) was found during flexion, extension and bending (P < 0.05). In bending and extension, a same result was recorded on the average pressure and max pressure of C3-4 facet joints (P < 0.05).

CONCLUSIONSThis study has demonstrated that the biomechanics at adjacent levels to a cervical spine fusion are altered and that there was progressively increased adjacent segment motion and stress as a single-level ACDF extended to a 3-level fusion, which might lead to the acceleration of adjacent segment degeneration.

Biomechanical Phenomena ; Cadaver ; Cervical Vertebrae ; surgery ; Diskectomy ; methods ; Humans ; Range of Motion, Articular ; Rotation ; Spinal Fusion ; methods

OBJECTIVETo investigate the influences of the distal femoral cut, the anterior and posterior femoral cuts, the proximal tibial cut on the dynamic alignment of the lower extremity in total knee arthroplasty.

METHODSBased on the three-dimensional geometric model, imitating the flexion movement of the knee without axial rotation after total knee arthroplasty, the influence of each of the three bone cuts on the dynamic alignment was analyzed with the assumption of standard bone cuts of the other two and equality of the medial and lateral soft tissue balancing. The dynamic alignment was defined as the angle between the mechanical axis of the tibia and the sagittal plane of the body when the knee was in any angle of flexion. With two of the three major bone cuts standard, the track of the tibial movement was established when the other one bone cut deviated from the ideal section of angle A. Based on the principle of geometry, the mathematical formula were established to present the influences of three bone cuts on the dynamic alignment of the lower extremity.

RESULTSAll of the three kinds of bone cuts in total knee arthroplasty influenced the dynamic alignment of the lower extremity not just in one static position, but during the whole range of motion. At the θ angle of knee flexion, the alignment of the lower extremity was arcsin(cosθsinA) when the varus/valgus femoral component alignment was A; the alignment of the lower extremity was arcsin(sinθsinA) when the rotational femoral component alignment was A; the alignment of the lower extremity was A when the varus/valgus tibial component alignment was A.

CONCLUSIONThe influences of the distal femoral cut, the anterior and posterior femoral cuts, the proximal tibial cut on the dynamic alignment of the lower extremity in total knee arthroplasty are dynamically changed during the flexion movement of the knee.

Arthroplasty, Replacement, Knee ; Femur ; surgery ; Humans ; Knee Joint ; Range of Motion, Articular ; Rotation ; Tibia ; surgery

OBJECTIVE: To establish animal models and investigate the impact of unilateral hemilaminectomy (ULHL) and different degrees of facetectomy (FT) on the cervical spinal biomechanics. METHODS: Twenty sheep were randomly and evenly divided into 4 groups. No operation was performed for group A, right C4-C6 ULHL was performed for group B, right C4-C6 ULHL and 50% ipsilateral C4-C5 FT was performed for group C, right C4-C6 ULHL and 100% ipsilateral C4-C5 FT was performed for group D. Animals of group A, B, C and D were sacrificed 24 weeks after operating and fresh cervical spine specimens were acquired, biomechanically tested and these data were compared to determine whether ULHL and different degrees of FT led to long-term differences in range of motion. RESULTS: (1) Changes of the total range of motion of cervical spine 24 weeks after surgery: the total range of motion of group D (60.2°±8.6°) was significantly greater than group A (40.7°±6.4°) and group B (41.2°±13.1°) under flexion-extension station, the total range of motion of group D (81.5°±15.7°) was significantly greater than that of group A (56.7°±12.2°) and group B (57.7°±12.8°) under lateral bending station, and the total range of motion of group D (38.5°±17.5°) had no obvious increase compared with group A (26.4°±9.9°) and group B (27.1°±10.9°) under axial rotation station. The total range of motion of group C had no obvious increase compared with group A and group B under flexion-extension station (44.1°±11.7°), lateral bending station (73.6°±11.4°) and axial rotation station (31.3°±11.5°). (2) Changes of the intersegmental motion 24 weeks after surgery: the intersegmental motion of group D (20.3°±4.6°) at C4-C5 was significantly greater than that of group A (11.7°±3.4°) and group B (11.9°±2.1°) under flexion-extension station, the intersegmental motion of group D (26.8°±3.5°) at C4-C5 was significantly greater than that of group A (15.2°±3.1°) and group B (16.2°±3.2°) under lateral bending station, the intersegmental motion of group D (15.2°±3.5°) at C4-C5 was significantly greater than that of group A (6.6°±2.3°) and group B (7.1°±1.9°) under axial rotation station. The intersegmental motion of group C (21.2°±4.1°) at C4-C5 was significantly greater than that of group A and group B under lateral bending station, the intersegmental motion of group C at C4-C5 had no obvious increase compared with group A and group B under flexion-extension station (15.7°±3.7°) and axial rotation station (10.3°±3.1°). CONCLUSION ULHL does not affect cervical stability, ULHL and 50% ipsilateral FT does not affect the long-term cervical stability, ULHL and 100% ipsilateral FT can lead to long-term instability under lateral bending and flexion-extension station.
Animals ; Biomechanical Phenomena ; Cervical Vertebrae ; Laminectomy ; Range of Motion, Articular ; Rotation ; Sheep

The present study was designed to examine the possible relationship between the function of the labyrinth and the role of the sympathetic nervous system In experimental motion sickness produced by rotatory movement(8O r.p.m.). The catecholamines in the brain, the heart and the adrenal gland of rats were rapidly reduced to one half of normal values following exposure to rotatory movement. The pretreatment with streptomycin and dramamine completely prevented the depletion by the rotatory movement of the catecholamines in the brain, the heart and the adrenal gland, but scopolamine did not prevent the decrease. Bretylium or chlorpromazine signifcantly inhibited reduction of the catechol-amines in both of the brain and the heart. However they did not influence the decrease in the adrenal gland. The reduction of the tissue catecholamines in rotatory movement is presumed to be caused largely by activation of the sympathetic nervous system mediated through labyrinthine stimulation.
Animals ; Catecholamines/*metabolism ; Labyrinth/*physiopathology ; Male ; Motion Sickness/*etiology ; Rats ; *Rotation ; Sympathetic Nervous System/*physiopathology ; OID - NASA: 70030571

The motions of humeral external rotation with and without the anterior band of inferior glenohumeral ligament complex (AB-IGHL) were simulated. As a result of comparison, the contact pressure and contact force are all higher when the AB-IGHL was included in the model. Therefore, it is theoretically proved that the AB-IGHL constrains the motion of humerus during humeral external rotation. The predicted values for von Mises and the maximum tense force in the AB-IGHL were 4.433 MPa and 37.32 N respectively, occurring on the humeral side of the ligament. This approach to evaluating the function of AB-IGHL would provide greater insight into the mechanical contribution of AB-IGHL to joint function, identify the mechanism of a hurt to AB-IGHL, and provide a quantitative means for developing low-risk rehabilitation protocols.
Finite Element Analysis ; Humans ; Ligaments, Articular ; physiology ; Range of Motion, Articular ; Rotation ; Shoulder Joint ; anatomy & histology ; physiology ; Tensile Strength

The purpose of this study is to show the correlation between the range of spinal motion and the severity of chronic lower back pain. The subjects of this study were 40 female patients with chronic lower back pain over a 6 months' duration. The range of spinal and hip joint motion was measured with a electrogoniometer, and the severity of back pain was evaluated with the Rolland's score and Pollard's pain disability index. Results were as follows. There was a correlation between the severity of pain and the range of lumbar lateral flexion, rotation, and extension (p< 0.05). Age, height, weight and body mass index had no correlation with the range of spinal motion. These results suggest that the range of lumbar spinal motion can be used as an objective measure for the evaluation of classifying chronic lower back pain patients and for planning and following their treatment.
Adult ; Back Pain/*physiopathology ; Chronic Disease ; Female ; Human ; Middle Age ; *Range of Motion, Articular ; Rotation ; Spine/*physiopathology ; Support, Non-U.S. Gov't

A comprehensive, geometrically accurate, nonlinear C0-T1 three-dimensional finite element (FE) model was developed for the biomechanical study of human cervical spine and related disorders. The model was developed with anatomic detail from the computed tomography (CT) images of a 46-year-old female healthy volunteer, and applied the finite element model processing softwares such as MIMICS13.1, Hypermesh11.0, Abaqus 6.12-1, etc., for developing, preprocessing, calculating and analysing sequentially. The stress concentration region and the range of motion (ROM) of each vertebral level under axial rotation, flexion, extension, and lateral bending under physiologic static loadings were observed and recorded. The model was proven reliable, which was validated with the range of motion in previous published literatures. The model predicted the front and side parts of the foramen magnum and contralateral pedicle and facet was the stress concentration region under physiological loads of the upper spine and the lower spine, respectively. The development of this comprehensive, geometrically accurate, nonlinear cervical spine FE model could provide an ideal platform for theoretical biomechanical study of human cervical spine and related disorders.
Biomechanical Phenomena ; Cervical Vertebrae ; Female ; Finite Element Analysis ; Humans ; Middle Aged ; Models, Biological ; Range of Motion, Articular ; Rotation